As one method for synthesizing liquid fuels from a natural gas, a GTL (Gas To Liquids: liquid fuel synthesis) technique of reforming a natural gas to produce a synthesis gas containing a carbon monoxide gas (CO) and a hydrogen gas (H2) as main components, synthesizing a synthesis oil (hereinafter referred to as “FT synthesis oil”) composed of a hydrocarbon mixture by using this synthesis gas as a source gas by the Fischer-Tropsch synthesis reaction (hereinafter referred to as “FT synthesis reaction”), and further hydroprocessing and fractionating the FT synthesis oil to produce liquid fuels and other products, such as naphtha (raw gasoline), kerosene, gas oil, and wax, has recently been developed. Since the liquid fuel products using this FT synthesis oil as a feedstock have high paraffin content, and almost no sulfur components, for example, as shown in Patent Document 1, the liquid fuel products attract attention as an environmentally friendly fuel. However, since special facilities are required in order to produce liquid-fuel products from the FT synthesis oil, utilization of the FT synthesis oil has been limited.
Additionally, since the FT synthesis oil obtained by the FT synthesis reaction contains a lot of normal paraffins, and has properties that the freezing point is high, and the fluidity is low, it is not possible to transfer FT synthesis oil by a pump, etc. at ambient temperature and it is difficult to handle the FT synthesis oil. Thus, Patent Document 2 suggests a technique of mixing this FT synthesis oil (FT wax) with a crude oil at a specific temperature, thereby uniformly dispersing the FT wax in the crude oil as fine crystals, forming a mixture which can be pumped at a surrounding temperature, and then transporting this mixture.